1. Field of the Invention
This invention is in the field of vehicle signal systems meant for and sent to people outside a vehicle to indicate changes in the vehicle's motion intended by the vehicle's operator. More particularly, the preferred embodiment of this invention is in the field of braking signals of the braking effort by a vehicle's operator.
2. Description of the Related Art
Anyone sharing a road with one or more other vehicles—particularly when those vehicles have drivers from different cultures—quickly realizes that what the most wants to know is what the other drivers intend to do. Much of the stress of driving arises from needing to know other drivers' intentions, in order to predict their future behavior and react before it is too late, but not getting signals that allow such prediction. Particularly, much of the stress of driving in ‘stop and go’ traffic arises from not being able to accurately gauge the braking intentions of a preceding vehiclc's driver or to signal changes in one's own braking effort to a following vehicle. All one can tell, and all one can indicate, is whether a driver is braking or not braking; but often, the question of import is whether a driver (whose brake lights are on) is braking harder, letting up, or maintaining a constant braking effort.
Because however much it helps to know what is happening to the other vehicle now, it is more important to know what probably will be happening in the future, particularly in the near future, when their behavior and yours may cause an (undesired) intersection. This places a great deal of emphasis on correctly comprehending any signal any other driver sends (and accurately sending a signal as to one's own behavior). Other, external cues (snow or rain falling, ice on the road, obstacles ahead, or the other vehicle's relative position and motion) can the perceived and judged directly as the other vehicle's present motion and position change. But a driver's intention and current effort (as distinct from the consequences of such effort) at present is poorly displayed. For example, a driver may be engaged in a hard braking effort, a medium braking effort, or a minimal braking effort, but only the fact that some braking effort is intended is displayed through the brake lights—which are the simplest, and most frequently misunderstood display. This need is particularly acute when, as at present in the United States, most vehicles on the road have automatic transmissions and so often apply their brakes not to slow the vehicle further, but to keep it from moving faster.
Under the present state of the art, brake signal systems (especially automobile brake signal systems) are strictly bi-modal; either they are off (no turn or braking is intended by the driver), or they are on. Many problems arise because this limited signal becomes overloaded.
Overloading can occur iii two ways. First, a signal may not adequately discriminate between differences; e.g. a signal (such as a set of brake lights) does not distinguish within the range of applied effort (e.g. does not signal differently for ‘hard braking’ and ‘soft braking’). All braking efforts are signaled as if they were identical in intention and result, though the control actually permits a wide range of braking potential. This can cause a following driver to run into a preceding vehicle if the following driver fails to realize that the previously soft-braking driver has had to slam on his brakes hard, and the failing driver fails to change his behavior and to brake as bard as the preceding driver. (The opposite error, of confusing ‘soft braking’ with ‘hard braking’ may also cause an accident—but this time between a following driver who unnecessarily slams on his brakes and the vehicle behind himself.)
Second, a signal may stay constant through a changed effort and thereby prevent other, possibly subtler signals, from being perceived. E.g. initial soft braking that suddenly becomes hard may create an accident if the following driver believes in the unchanging nature of the braking signal over the changing visual (or aural) cues indicating a decrease in separation distance resulting from the change in braking effort.
There have been prior efforts to improve on brake signal systems. Chiefly these have focused on linking the mechanical (or, more recently, the electronic-and-mechanical) aspects of the physical activity of the vehicle braking to the brake display. The inventors sought to make the brake lights reflect the actual braking behavior of the vehicle. In doing so, however, they forget two key factors: first, a signal is sent to a human being not to tell him what is happening to the vehicle, but to indicate what the other human intends to happen in the future; and, second, that human drivers can take in much more of the context in which the signaling vehicle is operating (namely, the external environment) and integrate that knowledge with a signal of another driver's intentions, to more accurately predict what the other vehicle is probably going to do, than any single display reporting only a vehicle's current state can accurately provide. Each driver needs to know more about what others intend than what is happening, because his response depends on prediction and reaction both—and part of that prediction must involve predicting what the other drivers will be doing, too, as his own intentions and behavior change!
In U.S. Pat. No. 5,231,373, Freeman et. al. alter the intensity of brake lights to match the alterations in the vehicle's velocity. Much of that patent focuses on trying to accommodate the problems in interpreting intensity arising from differential human physiology—bluntly, the fact that different folks see changes iii light intensity differently. This invention does not assure that a change in intensity will be consistent across vehicles, or manufacturers, i.e. does not do so in a fashion which readily indicates to a following driver where in the spectrum of possible intensities the current signal is located. Since different manufacturers could have different intensities (base, minimum, maximum, or any combination thereof), or, more realistically, manufacture different vehicles with different intensities, and the real world could readily give to identical vehicles different intensities, because of the different conditions and maintenance they have experienced or received (for example, the amount of dust or pollen currently on the light's surface), any following driver has no ready means to relate the absolute value of the current intensity to the intended effort. Moreover, it is far more difficult to determine relative intensity of a light display, than its physical size, even when not illuminated.
In U.S. Pat. No. 5,481,243, Lurie et. al. err in focusing on the behavior of the vehicle, rather than the intention of the driver. That invention has the same first flaw as Newton's, in focusing on the deceleration, rather than the braking effort, but it has a greater problem in that it defines deceleration by the change in the RPM of the vehicle's tires. Again, any “deceleration” caused by any reason is deemed to be intentional braking. Different types of errors can arise—for example, if the vehicle's tires cease to rotate, even though the vehicle is still moving, this would be read as a deceleration (and in fact, as a maximum deceleration). Which means that when the car ahead hits the ice or oil and skids, or water and hydroplanes, and the tires cease to rotate, the brake lights will go on at maximum—thereby increasing the probability that the driver behind, reading this as an intentional braking, will attempt to duplicate the effort, and brake at the worst possible moment, as he in turn hits the transient surface condition which caused the loss of traction. Another type of error this could cause is if the vehicle ahead is in loose traction (snow, ice, rain, sand, gravel, etc.) where the vehiclc's tires are alternately slipping over the surface, and thereby increasing their rotational speed but decreasing the forward motion, and then gripping, and decreasing the rotational speed—and thereby signaling ‘braking’—when in fact actual acceleration is taking place. Finally, this invention alters the intensity of the braking signal, as in Freeman, without resolving any of the aforementioned problems.
In U.S. Pat. No. 6,268,782, J. D. Newton teaches a device for signaling when deceleration increases. This invention contains several serious flaws. First, it confuses deceleration with braking. Going up a hill without adding pressure to the gam pedal will cause deceleration as will downshifting to a lower gear, or letting off on the gas pedal and being slowed by air resistance while shifting to a higher gear while continuing accelerating (the latter two may be more pronounced in a manual transmission). As a consequence, this invention would send a ‘false positive’ signal for each such deceleration indicating that the driver of the vehicle intended to brake. Second, this invention presumes that braking only increases—yet it often may be important to signal that braking is decreasing to avoid causing an overreaction. Third, since the invention requires learning a vehicle's maximum deceleration, it will automatically signal the maximum each time that the prior limit actually experienced is exceeded. This will create a false impression of reaching maximum deceleration too soon for any driver who does not put their car ‘through the paces’ and consciously practice a ‘panic stop’ (at some, and probably non-negligible cost to the tires, brake system, and nerves of the driver and surrounding citizenry) before taking it out onto the highway. This invention completely ignores the driver and leaves him with no role to play in signaling what he intends; it only signals what the vehicle is currently experiencing.
Driving is an analog art, control thereof is an analog effort, braking is an analog art, and brake signals should have an analog rather than a bimodal, binary display (‘on’ or ‘off’). What is needed is an analog signal that responds to and displays the braking intensity attempted and intended, that serves as a signal of the driver's intentions, and that allows ready comparison to the minimal and maximal braking effort in an intuitive fashion. While no invention can solve the separate problem of a driver sending the wrong signal (signaling a left turn and turning right), the invention described below frees the current state of the art braking display from the unnecessarily rigid, two-valued limits of the present implementation, and makes the braking signal responsive to the intended braking effort.